Re: [PATCH v9 08/12] migration/multifd: Add new migration option for multifd DSA offloading.

[Markus Armbruster <armbru@redhat.com>]

Yichen Wang <yichen.wang@bytedance.com> writes:

> From: Hao Xiang <hao.xiang@linux.dev>
>
> Intel DSA offloading is an optional feature that turns on if
> proper hardware and software stack is available. To turn on
> DSA offloading in multifd live migration by setting:
>
> zero-page-detection=dsa-accel
> accel-path="dsa:<dsa_dev_path1> dsa:[dsa_dev_path2] ..."
>
> This feature is turned off by default.
>
> Signed-off-by: Hao Xiang <hao.xiang@linux.dev>
> Signed-off-by: Yichen Wang <yichen.wang@bytedance.com>
> Acked-by: Dr. David Alan Gilbert <dave@treblig.org>

[...]

> diff --git a/qapi/migration.json b/qapi/migration.json
> index a605dc26db..76a3920e2e 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -629,10 +629,14 @@
>  #     multifd migration is enabled, else in the main migration thread
>  #     as for @legacy.
>  #
> +# @dsa-accel: Perform zero page checking with the DSA accelerator
> +#     offloading in multifd sender thread if multifd migration is
> +#     enabled, else in the main migration thread as for @legacy.
> +#
>  # Since: 9.0
>  ##
>  { 'enum': 'ZeroPageDetection',
> -  'data': [ 'none', 'legacy', 'multifd' ] }
> +  'data': [ 'none', 'legacy', 'multifd', 'dsa-accel' ] }
>  
>  ##
>  # @BitmapMigrationBitmapAliasTransform:
> @@ -840,6 +844,12 @@
>  #     See description in @ZeroPageDetection.  Default is 'multifd'.
>  #     (since 9.0)
>  #
> +# @accel-path: If enabled, specify the accelerator paths that to be

"If enabled" makes no sense, I'm afraid.

> +#     used in QEMU. For example, enable DSA accelerator for zero page

Please separate sentences with two spaces for consistency.

> +#     detection offloading by setting the @zero-page-detection to
> +#     dsa-accel, and defines the accel-path to "dsa:<dsa_device path>".

Looks like the members of the lists are strings in a little language you
invented, but are not defining here.

What is the abstract structure of the configuration data are you trying
to pass here?

> +#     This parameter is default to an empty list.  (Since 10.0)

Either "This parameter defaults to an empty list" or "(default empty
list)".

> +#
>  # @direct-io: Open migration files with O_DIRECT when possible.  This
>  #     only has effect if the @mapped-ram capability is enabled.
>  #     (Since 9.1)
> @@ -858,7 +868,7 @@
>             'cpu-throttle-initial', 'cpu-throttle-increment',
>             'cpu-throttle-tailslow',
>             'tls-creds', 'tls-hostname', 'tls-authz', 'max-bandwidth',
> -           'avail-switchover-bandwidth', 'downtime-limit',
> +           'avail-switchover-bandwidth', 'downtime-limit', 'accel-path',
>             { 'name': 'x-checkpoint-delay', 'features': [ 'unstable' ] },
>             'multifd-channels',
>             'xbzrle-cache-size', 'max-postcopy-bandwidth',

[...]